Fiber Optic Plates as Light Guides for Flat and Curved Scintillation Detectors

SPECT systems comprising arrays of modular scintillation cameras have long been recognized as an ideal approach for obtaining the dynamic data required for pharmacokinetic studies. As part of an effort to improve spatial resolution in scintillation detectors, we are investigating the use of fiber optic plates as a means to control the light spread in the light guide structure that transfers light from the scintillator exit surface to the light sensors. We have created a custom photon-transport code that handles the complexity of light propagation through fiber-optic cores as well as claddings to allow calculation of mean detector response functions (MDRFs) when combined with Monte Carlo simulations of gamma-ray interactions and lightsensor efficiency. We then invoke the Cramér-Rao Lower Bound derived from the Fisher-Information Matrix to estimate the intrinsic spatial resolution as a function of the optical design. We have simulated cameras with planar, cylindrically curved, and spherically curved scintillators and report on the efficacy of combining curved designs, which minimize parallax errors from pinhole projections, with fiber optic transfer plates that accomplish the transition from the curved scintillator to a planar array of light sensors. We assess the intrinsic 3D spatial resolution that can be achieved with maximum-likelihood (ML) estimation methods in these candidate modular camera designs, with the objective of arriving at a new version suitable for incorporation as the vertex camera in AdaptiSPECT-C, a project to develop a dedicated human brain imager.